Unveiling the Co2+ Ion Doping-Induced Hierarchical Shape Evolution of ZnO: In Correlation with Magnetic and Photovoltaic Performance

• Published in: ACS sustainable chemistry & engineering Vol. 5; no. 11; pp. 9981 - 9992
• Main Authors: Krishnapriya, R, Praneetha, S, Kannan, S, Vadivel Murugan, A
• Format: Journal Article
• Language: English
• Published: American Chemical Society 06.11.2017
• Subjects: Dye-sensitized solar cells; Microwave glycothermal; Hierarchical morphology; Zinc oxide nanocrystals; Cobalt doping
• ISSN: 2168-0485; 2168-0485
• DOI: 10.1021/acssuschemeng.7b01918

A sustainable, rapid microwave-assisted glycothermal (MW-GT) method has been adopted for the synthesis of pristine ZnO and a series of Zn1–x Co x O (x = 0, 0.02, 0.03, 0.05, 0.07, 0.10) within 15 min at 180 °C using ethylene glycol (EG) as solvent. The XRD results reveal that the altering of lattice parameters of ZnO by introduction of Co2+ ions and crystalline sizes of Co2+ doped ZnO samples decreased with increasing Co2+ ion content. A spectacular morphological change of ZnO from well-defined hexagonal prismoid to hierarchical flower-like 1-D nanorods-assembly upon increasing Co2+ ion concentration was perceived using FE-SEM and TEM analyses. After Co2+ ion inclusion into pristine ZnO, the width of the M–H loop significantly changes, where the diamagnetic behavior of ZnO changes from ferromagnetic to paramagnetic upon further increase in Co2+ ion content. Particularly, 5 mol % Co2+ ion doped ZnO sample shows enhanced photovoltaic performance in dye-sensitized solar cells (DSSCs) due to nanoscale level intermingling of two different 1-D nanorod-like morphology with particle-like morphology, resulting in size-mismatched combination-induced light-scattering effect, photoinduced charge-carrier formation by charge-transfer transitions of high spin Co2+ ions, and lower recombination resistance together with extended electron lifetime, which were deduced from UV–vis and impedance spectroscopy analysis, respectively.